Hermetically sealed wet electrolytic capacitor

ABSTRACT

A hermetically sealed wet electrolytic capacitor includes a hermetically sealed case, a cathode, an anode, and an insulator between the anode and the cathode to provide electrical insulation between the anode and the cathode. An electrolytic solution is disposed within the case. A first terminal is electrically connected to the anode and a second terminal is electrically connected to the cathode. The cathode comprises a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon. The electrolytic solution has a conductivity between 10 and 60 mS/cm. The capacitor may be used in an implantable device.

This application claims priority to U.S. Provisional Patent Application No. 61/169,764, filed on Apr. 16, 2009.

FIELD OF THE INVENTION

The present invention relates to capacitors, and more specifically to a capacitor suitable for use in medical applications such as implantable cardioverter defibrillators.

BACKGROUND

Capacitors are used in a wide range of electronic applications. Certain applications require a capacitor which is capable of a rapid electrical charge to a pre-determined voltage and, once charged, is also capable of delivering sizeable pulses of energy. One example of such an application is in implantable devices. In such an application, it is also important that the capacitor be compact in size and highly reliable.

Thus, what is needed is a capacitor suitable for use in applications, such as implantable cardioverter defibrillators, where reliability and performance are provided in a small size.

SUMMARY

Therefore, it is a primary object, feature, or advantage of the present invention to improve over the state of the art.

It is a further object, feature, or advantage of the present invention to provide a capacitor suitable for use in implantable devices.

A still further object, feature, or advantage of the present invention is to provide a capacitor that is capable of a rapid electrical charge to a pre-determined voltage and, once charged, is also capable of delivering sufficient pulses of energy to restore the normal function of a patient's heart when used in implantable cardioverter defibrillators (ICD).

Another object, feature, or advantage of the present invention is to provide a capacitor which is efficiently constructed and shaped to fit into the limited volume available within an ICD.

Yet another object, feature, or advantage of the present invention is to provide a capacitor with high performance and high reliability.

One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.

According to one aspect of the present invention, a hermetically sealed wet electrolytic capacitor is provided. The capacitor has a hermetically sealed case that encloses a cathode, an anode, an electrical insulator between the anode and the cathode and an electrolytic solution. A first terminal is electrically connected to the anode and a second terminal electrically connected to the cathode. The hermetically sealed wet electrolytic capacitor is able to provide a pulse delivery equal to at least 80 percent of the stored energy.

According to another aspect of the present invention, the capacitor's cathode includes a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon, and the electrolytic solution has a conductivity between 10 and 60 mS/cm.

According to another aspect of the present invention, a method of manufacturing a capacitor is provided. The method includes hermetically sealing a case containing an electrolytic solution having a conductivity between 10 and 60 mS/cm. The method further includes electrically connecting a first terminal to an anode, the anode being insulated from a cathode. The method further includes electrically connecting a second terminal to the cathode. The cathode is formed from a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a hermetically sealed wet electrolytic capacitor.

FIG. 2 illustrates the capacitor of FIG. 1 placed in an implantable cardioverter defibrillator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is now described with respect to a particular embodiment. That which is shown is merely for purposes of illustration and example, and one skilled in the art will understand that the present invention contemplates other options, alternatives, or variations.

FIG. 1 illustrates one embodiment of a capacitor 10 of the present invention. Although shown in a semi-circle shape, the capacitor 10 need not have such a shape. This particular shape is merely an example. In FIG. 1, a hermetically sealed wet electrolytic capacitor 10 is shown. The capacitor 10 has a hermetically sealed case 12. The capacitor 10 has a cathode 18 and an anode 16. One example design for an anode 16 would comprise sodium reduced capacitor grade tantalum powder pressed to a green density of between 5.0 and 7.0 grams/cc then vacuum sintered between 1450° C. and 1650° C. Powder, press and sinter conditions may be varied to attain the requisite capacitance. Formation of the anode should be in an electrolyte capable of sustaining the voltage necessary for the required oxide thickness.

An insulator 14, (preferably, but not required, comprising one or more layers of a polymeric material), is positioned between the anode 16 and the cathode 18 to electrically insulate the anode 16 from the cathode 18. An electrolytic solution 22 is disposed within the hermetically sealed case 12 and surrounds both the cathode 18 and the anode 16. The electrolytic solution 22 preferably comprises a gel which includes DI water, organic and inorganic acids and an organic solvent. The constituent components of the electrolytic solution 22 may be admixed in a variety of concentrations to provide conductivity within a preferred range between 10 and 60 mS/cm. One example of such an electrolytic solution 22 would be:

65-80% DI water

0.2-0.6% phosphoric acid

15-30% ethylene glycol

3-6% oxalic acid

2-4% boric acid

The cathode 18 is formed from a metal substrate 20 having an alloy layer 24 formed with a noble metal and a noble metal/base metal electrode element layer 26 electrochemically deposited on the alloyed surface from a solution of the metal salts. One example design for the cathode 18 may be a mixture of Pd and Cu electrodeposited on a Ti—Pd alloy. To increase adhesion of the cathode 18 to the alloyed substrate, an initial smooth film of Pd—Cu may be electrodeposited as a tacking layer. A rough, high surface area layer can then be deposited on top of the tacking layer to achieve a high capacitance cathode 18.

The metal substrate 20 of the cathode 18 can be formed of a valve metal. Examples of such valve metals include tantalum, niobium, hafnium, vanadium, zirconium, titanium or any of their alloys. The metal substrate 20 may have any number of shapes or configurations, including a planar or cylindrical shape. The metal substrate 20 may be a liner of any suitable shape and may represent a part of the capacitor case 12. Such a construction of the cathode 18 results in high cathode capacitance which assists in efficiently delivering energy stored in the capacitor 10 to a load.

A first terminal 30 is shown extending through a spacer 32. The first terminal 30 is electrically connected to the anode 16. A second terminal 36 is electrically connected to the cathode 18.

FIG. 2 illustrates one embodiment of an implantable cardioverter defibrillator (ICD) device 40. The device 40 includes the capacitor 10 of FIG. 1 (with a first terminal 30 and a second terminal 36), and a control circuit 42, which is electrically coupled to the capacitor 10, a detector 43 and a battery 44. The capacitor 10 is configured to provide a pulse delivery of at least 80 percent, (but preferably greater than 87 percent), of stored energy between the first and second terminals 30, 36. The detector 43 monitors a patient's condition and provides this patient data to the control circuit 42. The control circuit 42 monitors the information from the detector and upon detection of an anomaly or a critical condition, (which may be defined as one or more predetermined parameters that have exceeded one or more predetermined thresholds).

By way of example, the detector 43 may detect electrical activity in the heart of a patient and forward this data to the control circuit 42. The control circuit 42 monitors this electrical activity and if it drops below a certain electrical level, or if the electrical activity becomes irregular (as happens with an arrhythmia), initiates delivery of an electrical shock.

The battery 44 may be used to charge the capacitor 10 and to power the ICD device. The charging of the capacitor 10 may be constant (to counter the effects of charge leakage), such that the capacitor 10 is always ready for discharge; may be periodic (i.e. charging at predetermined intervals to keep the charge level of the capacitor 10 above a predetermined threshold); or may be on demand, such that when the onset of an anomaly is detected, the battery 44 is used to charge the capacitor at that time.

In the application of an ICD device 40, the capacitor 10 performs the function of delivering electrical shock therapy into the heart of a patient when a control circuit 42 of the ICD device 40 detects an anomaly or a critical condition in the patient. The capacitor 10 allows the capacitor to be capable of providing a rapid electrical charge to a pre-determined voltage, and thereafter delivering one or more pulses of sufficient energy to restore normal functions of a patient's heart.

The capacitor 10 as shown in FIG. 1 is efficient in nature and highly compact such that the capacitor 10 is constructed and shaped to fit within a limited volume within an ICD device 40. Preferably, the size of the capacitor 10 is 1.5-3.0 CC, and comprises a half-moon shape as shown in FIG. 1, although this should not be construed to be limiting to the present invention. The capacitor 10 is able to conform to any size and shape in order to fit the particular configuration demanded by the person within which it is being implanted.

In order to support the application of an ICD device 40, the capacitor 10 is able to supply a minimum of 9J, (but preferably 12J), upon demand. The amount of energy actually delivered is determined by the control circuit 42

A hermetically sealed wet electrolytic capacitor has been described. The present invention is not to be limited to the specific embodiment shown or described herein as the present invention contemplates variations in the size and shape of the capacitor, variations in the materials used, and other variations, alternatives, and options as would be apparent to one skilled in the art. 

1. A hermetically sealed wet electrolytic capacitor, comprising: a hermetically sealed case; a cathode having a first terminal; an anode having a second terminal; an insulator between the anode and the cathode for providing electrical insulation between the anode and the cathode; and an electrolytic solution disposed within the case; wherein the hermetically sealed wet electrolytic capacitor is adapted to delivery at least 80 percent of stored energy between the first and second terminals.
 2. The hermetically sealed wet electrolytic capacitor of claim 1 wherein the cathode comprises a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon.
 3. The hermetically sealed wet electrolytic capacitor of claim 2 wherein the metal substrate comprises a valve metal.
 4. The hermetically sealed wet electrolytic capacitor of claim 3 wherein the metal substrate comprises tantalum, niobium, hafnium, zirconium, titanium or alloys thereof.
 5. The hermetically sealed wet electrolytic capacitor of claim 1 wherein the electrolytic solution has conductivity between 10 and 60 mS/cm.
 6. The hermetically sealed wet electrolytic capacitor of claim 5 wherein the electrolytic solution comprises water, inorganic acids (phosphoric and boric), an organic acid (oxalic) and an organic solvent.
 7. An implantable device including the hermetically sealed wet electrolytic capacitor of claim
 1. 8. An implantable cardioverter defibrillator (ICD) including the hermetically sealed wet electrolytic capacitor of claim
 1. 9. An implantable device including: a battery; a processor coupled to the battery; and a capacitor coupled to the battery and the processor, including; a hermetically sealed case; a cathode including a first terminal; an anode including a second terminal; an insulator between the anode and the cathode which provides electrical insulation between the anode and the cathode; and an electrolytic solution disposed within the case having conductivity between 10 and 60 mS/cm; wherein the cathode comprises a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon; and whereby the capacitor is adapted to provide at least 80% of its stored energy between said first and second terminals in a single discharge.
 10. The hermetically sealed wet electrolytic capacitor of claim 9 wherein the metal substrate comprises a valve metal.
 11. The hermetically sealed wet electrolytic capacitor of claim 10 wherein the metal substrate comprise tantalum, niobium, hafnium, zirconium, titanium or alloys thereof.
 12. The hermetically sealed wet electrolytic capacitor of claim 9 wherein the electrolytic solution comprises water, inorganic acids (phosphoric and boric), an organic acid (oxalic) and an organic solvent.
 13. The hermetically sealed wet electrolytic capacitor of claim 9 being adapted to provide pulse delivery of at least 80 percent, preferably greater than 87 percent, of stored energy to the first and second terminals.
 14. An implantable device comprising the hermetically sealed wet electrolytic capacitor of claim
 9. 15. An implantable cardioverter defibrillators (ICD) comprising the hermetically sealed wet electrolytic capacitor of claim
 9. 16. A method of manufacturing a capacitor, comprising: hermetically sealing a case wherein an electrolytic solution being disposed within the case, the electrolytic solution having a conductivity between 10 and 60 mS/cm; electrically connecting a first terminal to an anode, the anode being insulated from a cathode; and electrically connecting a second terminal to the cathode, the cathode comprising a metal substrate having an alloy layer formed with a noble metal and a noble metal/base metal electrode element layer electrochemically deposited thereon.
 17. The method of claim 16 further comprising preparing the electrolytic solution by admixing water, inorganic and organic acids, and an organic solvent. 